For this computer exercise, you will use JavaBayes to create and use a small Bayesian network.
The JavaBayes home page, documentation, applet, and download are available.
You will model a small bayesian network that represents the relationship between yellow fingers, smoking, cancer, radiation, solar flares, and using a microwave.
In this model, smoking can cause yellow fingers and cancer. Solar flares and making microwave popcorn can cause radiation, and radiation can cause cancer as well.
The prior probability of smoking P(S) is 0.3. The prior probability of solar flares P(F) is 0.8. The prior probability of using the microwave is P(M) is 0.9.
The conditional probability table for radiation is
| F | M | P(R) |
| 0 | 0 | 0.1 |
| 0 | 1 | 0.2 |
| 1 | 0 | 0.2 |
| 1 | 1 | 0.9 |
The conditional probability table for cancer is
| S | R | P(C) |
| 0 | 0 | 0.1 |
| 0 | 1 | 0.6 |
| 1 | 0 | 0.3 |
| 1 | 1 | 0.9 |
The conditional probability table for yellow fingers is
| S | P(Y) |
| 0 | 0.11 |
| 1 | 0.8 |
Answer the following questions using JavaBayes
1. What is the prior probability of cancer?
2. What is the probability of smoking given cancer?
3. What is the probability of smoking given cancer and radiation?
4. Explain why knowing that radiation was present almost cancels the effect of knowing that cancer is present on the probability of smoking.
5. What is the markov blanket of yellow fingers?
6. Are solar flares and using the microwave independent given cancer?
7. What is the probability of cancer is you never use a microwave?
8. Is this a realistic model for predicting the probability of cancer? (if you think so, look at the American Cancer Society web site for actual statistics). Explain how the model could be improved.